Add admin API for group deletion

docs/admin_api/delete_group.md

+# Delete a local group
+
+This API lets a server admin delete a local group. Doing so will kick all
+users out of the group so that their clients will correctly handle the group
+being deleted.
+
+
+The API is:
+
+```
+POST /_matrix/client/r0/admin/delete_group/<group_id>
+```
+
+including an `access_token` of a server admin.

synapse/rest/client/v1/admin.py

@@ -784,6 +784,31 @@ class SearchUsersRestServlet(ClientV1RestServlet):
         defer.returnValue((200, ret))
 
 
+class DeleteGroupAdminRestServlet(ClientV1RestServlet):
+    """Allows deleting of local groups
+    """
+    PATTERNS = client_path_patterns("/admin/delete_group/(?P<group_id>[^/]*)")
+
+    def __init__(self, hs):
+        super(DeleteGroupAdminRestServlet, self).__init__(hs)
+        self.group_server = hs.get_groups_server_handler()
+        self.is_mine_id = hs.is_mine_id
+
+    @defer.inlineCallbacks
+    def on_POST(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        is_admin = yield self.auth.is_server_admin(requester.user)
+
+        if not is_admin:
+            raise AuthError(403, "You are not a server admin")
+
+        if not self.is_mine_id(group_id):
+            raise SynapseError(400, "Can only delete local groups")
+
+        yield self.group_server.delete_group(group_id, requester.user.to_string())
+        defer.returnValue((200, {}))
+
+
 def register_servlets(hs, http_server):
     WhoisRestServlet(hs).register(http_server)
     PurgeMediaCacheRestServlet(hs).register(http_server)
@@ -799,3 +824,4 @@ def register_servlets(hs, http_server):
     ListMediaInRoom(hs).register(http_server)
     UserRegisterServlet(hs).register(http_server)
     VersionServlet(hs).register(http_server)
+    DeleteGroupAdminRestServlet(hs).register(http_server)